塔里木河下游生态输水后植被景观格局动态变化研究

2000—2005年,塔里木河流域管理局先后7次向塔里木河下游断流区进行了生态输水,输水河道两岸的植被得到了一定的恢复.以2000—2005的中巴资源卫星CCD影像为主要数据源,获得了6a的植被/非植被二值图,并计算各年的景观格局指数,分析了6a植被景观格局的变化.结果表明:植被景观动态度在第四时段(2003—2004年)最大,为47.83%;在第三时段(2002—2003年)最小,为-1.39%;2000—2005年植被景观的动态变化呈正向趋势.2000—2005年,植被景观斑块个数与景观形状指数增加,蔓延度指数下降了36.9,斑块结合度指数均高于99,表明研究区的植被景观破碎化程度、分离程度增加,而景观类型联通性较高.植被斑块面积均处于增加趋势且远离河道植被恢复率越小,但植被景观的比重仍小于50%,说明非植被类型是研究区的基质类型,组成了景观的最大斑块.针对缓冲区Zone 1,植被景观的平均分维数处于减小趋势且2005年的斑块个数最小,斑块结合度指数处于增加趋势,表明近河道区域植被较为稳定,受生态输水的干扰度较小,植被景观斑块之间越来越聚集.6a间Zone 1的植被最大斑块指数均大于10%,远高于其它5个缓冲带,表明离河道越近植被景观的优势度最大.

Changes in Landscape Pattern in the Lower Reaches of Tarim River after an Ecological Water Delivery

In the period from 2000 to 2005,the vegetation along the previously dried section of the Tarim River recovered due to the seven separate ecological water deliveries from the Dashkol Reservoir in the lower reaches of the river.In this paper,binary annual vegetation maps involving vegetated and non-vegetated areas were produced based on CBERS/CCD images from 2000 to 2005 using GIS and remote sensing techniques,and landscape indices were computed to analyze the changes in vegetation landscape pattern using the FRAGSTATS software.Results showed that the maximum of vegetation landscape dynamics was 47.83% over the period from 2003 to 2004,while the minimum of it was-1.39% during the period from 2002 to 2003,indicating a vegetation recovery trend during the whole study period.Number of vegetation patches and the landscape shape index also increased,while the contagion index decreased by 36.9.The patch cohesion index became greater than 99 over the whole study period,which implies that landscape fragmentation and dispersion increased,with a higher connectivity of landscape types.Moreover,the average area of vegetation patches increased and the percentage of the recovered vegetation area was negatively related to the distance from the river channel.However,the vegetated landscape occupied still less than 50% of the study area.Remainder of the area was non-vegetated,including takir desert,bare soil and sandy desert,forming the major landscape types in the study area.In buffer zone 1,the minimum fractal dimension of vegetation landscape decreased,the number of patches became a minimum in 2005,and the patch cohesion index increased,which indicated that the vegetation near the river channel was stable and less disturbed by the ecological water delivery,and the patches of vegetation landscape became more concentrated.In buffer zone 1,the largest patch index was always greater than 10%,much higher than those in other buffer zones over the whole study period,suggesting that the vegetation landscape near by the river channel has more ecological dominance.